Fastener
It is known to use screws to fasten cladding to the structural timber framing of a building. A problem is that in an earthquake event, movement of the wall can cause the screws to bend and cause non-recoverable damage to the cladding and framing. This may adversely affect the ability of a building to absorb energy sufficient to resist the destructive forces that earthquakes bring to bear. The fasteners address this problem. The fastener has a head 2, a first shaft portion (a fuse) 4 and a second shaft portion (a shank) 5. The fuse extends between the head and the shank and has less resistance to bending than the shank.
This invention relates to a fastener, for example a screw fastener for use in securing internal or external sheet cladding or other components in a building.
BACKGROUNDIt is known in the context of construction to fasten cladding to the structural timber framing of a building with screws. A problem with this is that during an earthquake movement of the wall can cause the screws to bend and thereby cause non-recoverable damage to the cladding and timber framing surrounding the screw. This may adversely affect the ability of a building to absorb energy sufficient to resist the destructive forces that earthquakes bring to bear. One solution is to more heavily engineer a building to provide it with more or longer bracing walls than may be desirable. However, this tends to adversely increase the costs of construction.
OBJECT OF THE INVENTIONIt is an object of preferred embodiments of the invention to go at least some way towards addressing the above problem. While this applies to preferred embodiments, the object of the invention per se is simply to provide a useful choice. Therefore, any objects or advantages applicable to preferred embodiments should not be taken as a limitation on claims expressed more broadly.
DefinitionsThe term “comprising” or “has”, as used in this document in relation to a series of features, means they are present as a minimum combination but does not rule out the option of there being additional features. The same applies to related terms such as “comprises” or “having”.
SUMMARY OF THE INVENTIONAccording to one aspect of the invention there is provided a fastener (preferably for installation in timber) comprising—
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- a head;
- a first shaft portion (a fuse); and
- and a second shaft portion (a shank);
formed such that the fuse extends between the head and the shank and has less resistance to bending than the shank.
Optionally the fastener is in the form of a screw in which at least the shank is screw threaded.
Optionally the fastener has a force spreading liner that has an opening large enough to allow the fuse and shaft to pass through, but not large enough to allow the head to pass through.
Optionally the liner is wider than the head.
Optionally the liner comprises a cup that is adapted to receive the head completely within the cup.
Optionally the fastener is used to hold a cladding sheet to wall framing of a building, arranged such that—
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- the head is located at or adjacent to an outer face of the cladding sheet;
- the fuse extends in the cladding sheet; and
- the shank extends in the wall framing.
Optionally the fastener is in the form of a screw in which at least the shank is screw threaded.
Optionally the fastener is used to hold a sheet of cladding to wall framing of a building, and is arranged such that—
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- the head is located at or adjacent to an outer face of the cladding and substantially within or against the liner;
- the fuse extends in the cladding; and
- the shank extends in the wall framing;
the arrangement being such that in the event the head is caused to tilt with respect to the cladding it impinges on the liner and not the cladding.
Optionally the liner comprises a plate that is wider than the head.
Optionally the liner comprises a cup and the head is completely within the cup.
Optionally the liner is partially or completely recessed in the cladding.
Optionally the head is inside the exterior surface of the cladding.
Optionally the fuse is thicker immediately adjacent to the head.
Optionally the shank is thicker and is non-threaded immediately adjacent to the fuse.
Optionally the shank is thicker and is threaded immediately adjacent to the fuse.
Optionally the thicker part of the shank immediately adjacent the head is fitted in a pre-formed or self-drilled hole in the framing.
Optionally the cladding is 7 mm to 24 mm thick.
Optionally the cladding comprises plaster board or plywood.
Optionally an exterior face of the cladding has a surface area of at least 2 m2.
Optionally 0% to 100% of the length of the fuse is within the cladding.
Optionally 20% to 100% of the length of the shank is within the cladding.
Optionally the fuse is able to withstand a lateral force of 0.5 KN to 5 KN (or 1-4 KN or 2-3 KN).
Optionally the thread stops short of a proximal end of the shank but extends to a distil end of the shank.
Optionally the fuse is substantially narrower than the shank.
Optionally the fuse is 2.5 mm to 10 mm wide and the shank is 5 mm to 10 mm wide (eg as diameter).
Optionally the fastener is installed in framing to secure cladding such that there is space around the fuse such that a portion of the fuse is able to move unobstructed within that space in the event of an earthquake.
Optionally the space around the fuse has been created as a hole drilled through the cladding before installation of the fastener.
Optionally the liner has been rotated to cause a consequential adjustment to bending resistance of the fuse.
Some preferred embodiments of the invention will now be described with reference to the accompanying drawings, of which:
Referring to
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By way of example and for contrast,
Referring again to
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In some embodiments of the invention the fastener 1 may be made or used with any single or any combination of the following parameters—
While preferred embodiments have been described above for one fastener 1, it will be appreciated that in practice multiple of these would be used spaced out for each sheet of cladding.
In some embodiments of the invention the effective lateral seismic capacity of the fastener 1 may be adjusted on-site without needing to modify it. For this, the liner 7 may simply be rotated on installation by varying degrees, up to a maximum of 90 degrees. This can alter the moment developed by the head 2 when under load. In some embodiments small fins that are aligned to the axis of the fastener may be used on the outside of the liner 7. They serve to prevent undesired rotation of the liner, with unintentional alteration to the capacity “setting” of the liner 7.
Preferably the floor of the liner 7 is capacity designed to yield and shed load before the fastener pulls out of the framing 11. By way of example, the amount of effective axial shortening of the fastener may be 1.4 mm when it reaches 6 mm lateral travel.
Referring to
The liner 7 may serve to minimise “popping” of the cladding, i.e. where a prior art fastener (as per
Preferably a hole is pre-drilled in the framing 11 just below the liner 7 (optionally 16 mm-20 mm diameter), this being deep enough to provide for free lateral movement of the fuse 4 by up to 8 mm without engaging the timber at the side of the hole as the cladding 10 slides relative to the framing 11. However the hole is not formed so deep as to reduce the effectiveness of the enlarged section 5a bearing laterally on the framing (see
In a further embodiment of the invention the design may be such that if the fastener is unable to yield, for example because part of the fastener bears against the hole in the framing and so its effective capacity increases beyond that designed for, then another part of the system may yield to compensate for this. For example hold-down brackets may be used at the ends of the sheets of the cladding and these may ‘flex or otherwise “give’, in place of the fuse.
In some embodiments of the fastener 1 the fuse may be further ‘necked’ (i.e. with a reduced width) to reduce its load capacity to a desired level, optionally near the head of the screw. Alternatively, the fuse may be enlarged slightly near the shank 5 to match a reducing moment profile over the length of the fastener, and so spread ‘plastic strain’ over a greater distance. This can serve to produce better plastic action and reduce the risk of low cycle fatigue. To elaborate, if the fuse is narrow-necked near the fastener's head, the moment capacity of the fuse will be correspondingly reduced. This in turn can reduce an undesired unpredictable moment near the fastener's head due to restraint of the head. It does not apply in the case of the ledges 9 because in that instance the joint between the head 2 and liner 7 is effectively, at least nearly, a theoretical ‘pin’. Conversely, a progressive enlargement of the diameter of the fuse results in a near constant flexural strain along the fuse at the critical point near the shank 5. The above distribution of strain is preferable as the fuse is better able to complete multiple strain cycles before rupturing.
In some embodiments, the upper opening into the liner 7 may be left without a skim of plaster so as to not restrict rotation of the head 2 which may otherwise lead to a greater risk of damage in an earthquake. Instead, an alternative material such as a flexible ‘paint-over’ sealant may be used, which allows for rotation of the head 2 more freely than a skim of plaster. Optionally a small removable plug may be inserted in the opening of the liner, e.g. in the screw driver slot 3 (see
Optionally, in preferred embodiments of the fastener 1, rotation of the head 2 causes a measurable outward movement of the face of the wall. The degree of movement may provide information to an engineer as to the extent of damage and/or movement in an earthquake.
In some embodiments of the invention the fastener may be produced to give heavy duty performance, for example to attach metal to wood. In this case the fastener may be made to resist approximately 3.4 KN of lateral load. It may incorporate all the same features including the fuse, an enlarged section immediately beyond the fuse (e.g. the part 5a of
In other embodiments of the invention the fastener 1 may be used, with or without the liner 7, for fixing joining plates on portal frames, or for joining timber beams and columns with plates in a multi-storey build, optionally possibly in conjunction with a pre-stressing system.
Although in preferred embodiments of the invention the fastener 1 is screw threaded, for example as a coach screw or bolt, in other embodiments it may have no thread. In that case the fastener may be in the form of a nail that is applied in a predrilled hole in the framing.
While some preferred embodiments of the invention have been described by way of example it should be appreciated that modifications and improvements can occur without departing from the scope of the following claims.
In terms of disclosure, this document hereby discloses each item, feature or step mentioned herein in combination with one or more of any of the other item, feature or step disclosed herein, in each case regardless of whether such combination is claimed.
Claims
1. A fastener comprising— formed such that the fuse extends between the head and the shank and has less resistance to bending than the shank.
- a head;
- a first shaft portion (a fuse); and
- and a second shaft portion (a shank);
2. A fastener according to claim 1, in the form of a screw in which at least a portion of the shank is screw threaded.
3. A fastener according to claim 2, comprising a force spreading liner that has an opening large enough to allow the fuse and shaft to pass through, but not large enough to allow the head to pass through.
4. A fastener according to claim 3, wherein the liner is wider than the head.
5. A fastener according to claim 4, wherein the liner comprises a cup that is adapted to receive the head completely within the cup.
6. A fastener according to claim 1, when used to hold a cladding sheet to wall framing of a building, arranged such that—
- the head is located at or adjacent to an outer face of the cladding sheet;
- the fuse extends in the cladding sheet; and
- the shank extends in the wall framing.
7. A fastener according to claim 6, in the form of a screw in which at least the shank is screw threaded.
8. A fastener according to claim 3, when used to hold a sheet of cladding to wall framing of a building, arranged such that— the arrangement being such that in the event the head is caused to tilt with respect to the cladding it impinges on the liner and not the cladding.
- the head is located at or adjacent to an outer face of the cladding and substantially within or against the liner;
- the fuse extends in the cladding; and
- the shank extends in the wall framing;
9. A fastener according to claim 8, wherein the liner comprises a plate that is wider than the head.
10. A fastener according to claim 8, wherein the liner comprises a cup and the head is completely within the cup.
11. A fastener according to claim 8, wherein the liner is partially or completely recessed in the cladding.
12. A fastener according to claim 8, wherein the head is inside the exterior surface of the cladding.
13. A fastener according to claim 7, wherein the fuse is thickest immediately adjacent to the head.
14. A fastener according to claim 1, wherein the shank is at its thickest and is non-threaded immediately adjacent to the fuse.
15. A fastener according to claim 1, wherein the shank is at its thickest and is threaded immediately adjacent to the fuse.
16. A fastener according to claim 8, wherein the cladding comprises plaster board or plywood.
17. A fastener according to claim 1, when installed in framing to secure cladding such that there is space around the fuse such that a portion of the fuse is able to move unobstructed within that space in the event of an earthquake.
18. A fastener according to claim 5, wherein:
- the fastener is holding cladding sheet to wall framing of a building;
- the head is completely within the cup;
- the fuse is thicker immediately adjacent to the head than it is immediately adjacent to the shank;
- the head is located at or adjacent to an outer face of the cladding sheet;
- the fuse extends in the cladding sheet;
- the shank extends in the wall framing;
- the liner is recessed in the cladding; and
- Zo the head is inside the exterior surface of the cladding.
19. A fastener according to claim 18, wherein the cladding sheet is a sheet of plywood.
20. A fastener according to claim 4, wherein:
- the fastener is holding cladding sheet to wall framing of a building;
- the head is on the outside of the liner;
- the fuse is thicker immediately adjacent to the head than it is immediately adjacent to the shank;
- the head is located at or adjacent to an outer face of the cladding sheet;
- the fuse extends in the cladding sheet;
- the shank extends in the wall framing; and
- the liner is engaged in the cladding.
21. A fastener according to claim 20, wherein the cladding sheet comprises a sheet of plywood.
22. A fastener according to claim 6, wherein the fuse is substantially narrower than the shank.
23. A fastener according to claim 1, wherein the fuse is substantially narrower than the shank.
24. A fastener according to claim 6, arranged such that rotation of the liner will cause a consequential adjustment to bending resistance of the fuse.
Type: Application
Filed: Jun 1, 2022
Publication Date: Dec 22, 2022
Inventor: Roy George Taylor (Wellington)
Application Number: 17/830,267